Alternative RNA splicing is an essential mechanism to regulate gene expression and generate proteome diversity. It is estimated that 60% of human genes are alternatively spliced, and many genes are spliced to yield hundreds or thousands of different mRNAs. Furthermore, misregulation of alternative splicing has been implicated in many diseases, including cancer. Understanding the regulation of splice site choice and the functions of splice variants is critical for the elucidation of many cellular processes. Alternative splicing is more abundant in the nervous system than any other tissue, but little is understood about how splicing in neurons is controlled. The broad objective of this proposal is to understand how the regulation of alternative splicing plays a role in neuronal development. It has been demonstrated that the polypyrimidine tract binding protein (PTB) represses neural-specific alternative splicing, and one hypothesis is that PTB repression is removed in order to enhance neural splicing patterns. Recently, a neuronal homologue of PTB (nPTB) was identified. Evidence indicates there is a switch in the expression from PTB to nPTB during neuronal differentiation, and this switch could have a significant impact on the control of neuronal splicing and development. Using cellular, molecular, and genomics approaches, the aims of this proposal are to (i) characterize the expression profiles of PTB and nPTB during neuronal development, (ii) identify RNA targets of nPTB, and (iii) demonstrate how nPTB-regulated splicing events affect neuronal differentiation. These studies will help to understand how alternative splicing is controlled in the nervous system and how changes in splicing may be central to the programming of neuronal development. [unreadable] [unreadable]